Inert gas fire suppression systems are often used to protect equipment that can get damaged by use of traditional suppression systems that use water, foams and powders. For example, inert gas fire suppression systems can be used to protect electronic equipment such as, e.g., personal computers, servers, equipment found in large data storage centers, and network switches to name just a few. A typical fire suppression system includes a high pressure inert gas source that is connected to one or more inert gas discharge nozzles via piping. A given fire suppression nozzle has an effective protection height and a maximum coverage area, i.e., the area in which the nozzle is effective in suppressing a fire. Depending on the area of coverage, one or more of the nozzles are installed in an enclosed space to protect the enclosure. In case of a fire, a detector triggers the system and a control valve is opened to send high pressure inert gas to the nozzles. Depending on the system, the high pressure source can be connected to more than one enclosure, through pipe network ending in multiple nozzles, and the flow to each enclosure is individually controlled via respective control valves.
Industry regulations require that the fire suppression systems meet certain standards. For example, “NFPA 2001: Standard on Clean Agent Fire Extinguishing Systems,” 2015 Edition (hereinafter “NFPA 2001”), which is incorporated herein by reference in its entirety as background, provides the requirements for clean agent fire extinguishing systems. Section 5.8 of NFPA 2001 generally states that the nozzle needs to be designed for the intended use and selected based on the limitations concerning size of the enclosure, the floor coverage and alignment. Section 5.4.2 of NFPA 2001 requires that the method for flame extinguishment and the suppression agent concentration conform to ANSI/UL 2127, “Standard for Inert Gas Clean Agent Extinguishing System Units,” Second Edition (hereinafter “UL 2127”), which is incorporated herein by reference in its entirety as background. UL 2127 states that the extinguishing system must suppress the fire within 30 seconds after completion of agent discharge and provides requirements on the construction of the test enclosure and the locations in the enclosure for measuring the agent concentration. According to UL 2127, the test enclosure to be constructed must have the maximum area coverage for the extinguishing system or nozzle and the minimum and maximum protected area height limitations. Thus, each fire suppression nozzle that is compliant with UL 2127 is rated for a maximum area coverage and a minimum/maximum protection height.
In order for the fire suppression nozzle to provide the coverage area and protection height and reduce the oxygen content in the enclosure in compliance with UL 2127, a large amount of inert gas is discharged into the enclosed area in a short period of time. To accomplish this, typically, the inert gas suppression systems often discharge the inert gas at supersonic velocities. The supersonic velocities create significant turbulence, resulting in a high power broadband spectrum of sound. That is, the high velocity gas flowing from the inert gas discharge nozzles can result in very high levels of sound. However, certain electronic components with sensitive mechanical parts (e.g., hard disc drives) are susceptible to adverse effects from high levels of sound. The high sound levels can reduce the performance of these components, and in some cases, the components may stop functioning altogether. Although the computer equipment can be shut down to protect the sound sensitive components, in many cases, if the enclosure houses critical computer systems where downtime is unacceptable due to, e.g., economic or safety reasons, the computer equipment is kept operational even while the nozzle discharges the inert gas. Thus, while electronic equipment in an enclosure may be unaffected by the fire itself, the equipment can still experience damage and thus downtime due to the high sound levels from the inert gas discharge.
Previous attempts in the industry to reduce the high levels of sound associated with the high velocity/high pressure gas discharge have primarily dealt with restricting the flow rate of gas into the enclosed area. For example, previous designs have included blocking the flow inside the nozzle using sound absorbing materials. However, to effectively reduce the sound level of the gas to an acceptable range, e.g., to levels that prevent hard disk failures, the flow rate needs to be significantly reduced, which typically means a high pressure drop in the nozzle. The resulting reduction in the flow rate prevents the gas from being discharged fast enough to quickly reduce the oxygen level and meet current fire suppression standards. Thus, previous attempts to reduce the sound output of the fire suppression nozzles have resulted in a decreased effective coverage for the nozzle. That is, in an attempt to produce a reduced-sound nozzle, the related art nozzles have decreased the maximum coverage area and/or the maximum protection height. Accordingly, a greater number of the related art reduced-sound nozzles may be needed in order to have the same coverage area as existing fire suppression nozzles. In addition, because the coverage area is less, the related art reduced-sound nozzles cannot directly replace, i.e., retrofit, existing fire suppression nozzles that have already been installed in enclosures without substantial modifications to the system, e.g., by running new piping to install additional nozzles.
Accordingly, there is a need for fire suppression nozzles that can quickly discharge gases and reduce the sound generated during discharge to acceptable levels for electronic equipment. In addition, there is also a need to retrofit existing fire suppression nozzles with reduced-sound nozzles without substantial modifications to the existing systems. Further limitations and disadvantages of conventional approaches to inert gas nozzle configurations will become apparent to one skilled in the art through comparison of such approaches with embodiments of the present invention as set forth in the remainder of the present disclosure with reference to the drawings.